LSH hamster model of syphilitic infection and transfer of resistance with immune T cells

Laboratory diagnosis and interpretation of tests for syphilis

The lack of a method for demonstrating the presence of Treponema pallidum by growth necessitates the use of alternative methods. Traditionally, these methods are divided into direct detection methods (animal inoculation, dark-field microscopy, etc.) and serologic tests for the presence of patient antibody against T. pallidum. Serologic methods are further divided into two classes. One class, the nontreponemal tests, detects antibodies to lipoidal antigens present in either the host or T. pallidum; examples are the Venereal Disease Research Laboratory and rapid plasma reagin and tests. Reactivity in these tests generally indicates host tissue damage that may not be specific for syphilis. Because these tests are easy and inexpensive to perform, they are commonly used for screening, and with proper clinical signs they are suggestive of syphilis. The other class of test, the treponemal tests, uses specific treponemal antigens. Confirmation of infection requires a reactive treponemal test. Examples of the treponemal tests are the microhemagglutination assay for antibodies to T. pallidum and the fluorescent treponemal antibody absorption test. These tests are more expensive and complicated to perform than the nontreponemal tests. On the horizon are a number of direct antigen, enzyme-linked immunosorbent assay, and PCR techniques. Several of these techniques have shown promise in clinical trials for the diagnosis of congenital syphilis and neurosyphilis that are presently difficult to diagnose.

Experimental model of congenital syphilis

Female LSH hamsters infected with Treponema pallidum subsp, endemicum before pregnancy or during early pregnancy transmit a form of syphilis to the fetus that is similar to human congenital syphilis. The offspring develops rhinitis, skin rash, failure to thrive, and hepatosplenomegaly. T. pallidum is detectable in their livers, spleens, and nasal secretions. Immunoglobulin M antibodies are detected in the serum.

Clarithromycin therapy of experimental Treponema pallidum infections in hamsters

Clarithromycin was shown to be effective therapy for Treponema pallidum infections in hamsters. Clarithromycin therapy was effective when initiated either 1 or 8 days after infection. The delay in initiation of therapy allowed an active infection to develop. The treponemal burden in lymph tissue of treated hamsters was eradicated, as determined by dark-field microscopy and by inoculation of lymph material into susceptible hamsters. Treatments with clarithromycin and the 14-hydroxy metabolite of clarithromycin were equally effective. Therapy with clarithromycin and penicillin was not antagonistic and did not appear to be synergistic when the two drugs were given concurrently. Pharmacokinetic evaluation of clarithromycin in hamsters showed that the doses which produced effective therapy yielded concentrations in serum similar to those routinely achieved in human sera. These findings demonstrate that clarithromycin is effective in treating active or incubating syphilis in the hamster model and could be useful in treating humans.

Ability of macrophages to process and present Treponema pallidum Bosnia A strain antigens in experimental syphilis of syrian hamsters

The ability of macrophages to process and present treponemal antigens to T-lymphocytes was studied in early stages of experimental syphilis produced by Treponema pallidum Bosnia A strain (the causative agent of endemic syphilis) infection of inbred Syrian hamsters (LSH/Ss Lak strain). A difference was noticed in the response of macrophages obtained from the peritoneal cavity, lymph nodes, and spleens of the infected animals. In all of these locations, a general increase in the population of Ia(k)-positive macrophage was seen during the entire period of infection, i.e., 3 to 18 weeks after inoculation. Peritoneal cavity-derived macrophages showed no difference in antigen presentation to sensitized and nonsensitized T-lymphocytes for the first 7 weeks of infection. However, at 18 weeks after infection, peritoneal macrophages lost their ability to process treponema antigens. Spleen- and lymph node-derived macrophages did not exhibit a parallel loss in their ability to process treponema antigens. A fluctuation without a consistent pattern was noticed in the antigen processing and presentation by macrophages from the spleen and lymph nodes. In general, the sensitized T-lymphocytes responded to treponema antigen presented by macrophages more vigorously than the nonsensitized T-lymphocytes. An increased ability of spleen-derived macrophages to process and present antigens was noticed throughout the entire period of infection. The macrophages from the lymph nodes showed such an increase only temporarily at 3 weeks after infection. These data suggest that the processing and presentation of treponema antigens by macrophages in acute syphilitic infection fluctuates considerably and depends on the source of macrophages and the duration of the infection. The differences in the response of peritoneal cavity-, spleen-, and lymph node-derived macrophages probably reflect the complex interactions between the macrophage and other cells involved in the immune response to treponema infection.